Even the chair of the 9/11 Commission now admits that the official evidence they were given was far from the truth.

Six years after 9/11, the American public have still not been provided with a full and truthful account of the single greatest terror attack in U.S. history.

What they got was a turkey. The 9/11 Commission was hamstrung by official obstruction. It never managed to ascertain the whole truth of what happened on September 11 2001.

The chair and vice chair of the 9/11 Commission, respectively Thomas Kean and Lee Hamilton, assert in their book, Without Precedent, that they were set up to fail and were starved of funds to do a proper investigation.

They also confirm that they were denied access to the truth and misled by senior officials in the Pentagon and the federal aviation authority; and that this obstruction and deception led them to contemplate slapping officials with criminal charges.

Despite the many public statements by 9/11 commissioners and staff members acknowledging they were repeatedly lied to, not a single person has ever been charged, tried, or even reprimanded, for lying to the 9/11 Commission.

From the outset, the commission seemed to be hobbled. It did not start work until over a year after the attacks. Even then, its terms of reference were suspiciously narrow, its powers of investigation curiously limited and its time-frame for producing a report unhelpfully short — barely a year to sift through millions of pages of evidence and to interview hundreds of key witnesses.

The final report did not examine key evidence, and neglected serious anomalies in the various accounts of what happened. The commissioners admit their report was incomplete and flawed, and that many questions about the terror attacks remain unanswered. Nevertheless, the 9/11 Commission was swiftly closed down on August 21 2004.

I do not believe in conspiracy theories. I prefer rigorous, evidence-based analysis that sifts through the known facts and utilizes expert opinion to draw conclusions that stand up to critical scrutiny. In other words, I believe in everything the 9/11 Commission was not.

The failings of the official investigation have fuelled too many half-baked conspiracy theories. Some of the 9/11 truth groups promote speculative hypotheses, ignore innocent explanations, cite non-expert sources and jump to conclusions that are not proven by the known facts. They convert mere coincidence and circumstantial evidence into cast-iron proof. This is no way to debunk the obfuscations and evasions of the 9/11 report.

But even amid the hype, some of these 9/11 groups raise valid and important questions that were never even considered, let alone answered, by the official investigation. The American public has not been told the complete truth about the events of that fateful autumn morning six years ago.

What happened on 9/11 is fundamentally important in its own right. But equally important is the way the 9/11 cover-up signifies an absence of democratic, transparent and accountable government. Establishing the truth is, in part, about restoring honesty, trust and confidence in American politics. . . .